Many devices and systems contain pressurized substances, such as fluid and gas. In such devices and systems, measurement or indication of pressure is often desirable. For example, an indication of proper tire pressure is desirable for safety and longevity of the tire and an indication of conduit pressure may be desirable prior to disconnecting the conduit or may allow circuit analysis and diagnosis when the conduit is a component of a pressurized circuit.
Heretofore, pressure in a device or circuit has typically been indicated through use of various gauges known in the art. Such pressure gauges are typically provided with a scale or dial for measuring or indicating pressure. In addition to being costly, performance and accuracy of pressure gauges may be affected by a number of factors, including temperature, leakage, vibration, condensation, fluctuations in pressure, corrosion, and clogging. In situations where a pressure gauge generates inaccurate readings, it may be difficult determine whether the reading is inaccurate, unless one or more other accurate pressure gauges are also used to measure the pressure. Accordingly, pressure gauges may not always be relied on for accurately indicated pressure.
Although pressure gauges that use a scale or dial are common, pressure indicators have been developed that use color to indicate or measure pressure; however, they have not been widely adopted. An example of such a pressure indicator is found in U.S. Pat. No. 5,189,979 to Popenoe (hereinafter referred to as “Popenoe”). In Popenoe, the pressure indicator includes a light absorbing fluid located between a diaphragm and a viewing window. On the side of the diaphragm facing the viewing window, a color indicating area is provided. An increase in pressure causes the diaphragm to flex and the indicator to be displaced toward the viewing window, thereby decreasing the thickness of the light absorbing fluid between the color indicator and the viewing window. As a result the color indicating area may be viewed through the viewing window.
The present invention is directed at devices that include a mechanochromatic material that changes color in response to pressure.